Derping With Kotlin
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The document introduces Kotlin programming concepts such as variables, functions, classes, null safety, collections, and domain-specific languages. It provides code examples to demonstrate Kotlin syntax for these concepts, including defining variables and functions, creating and using classes, handling null values, mapping collections, and building internal domain-specific languages.
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Derping With Kotlin
- 5. // JVM // Android // JavaScript // LLVM
- 6. // Actually has libraries // Actually has tooling // Actually has traction
- 7. // Variables
- 8. val name = "Ross" var age = 32
- 9. val name: String = "Ross" var age: Int = 32
- 10. val name = "Ross" var age = 32
- 11. // Functions
- 12. fun answer(): Int { return 42 }
- 13. fun answer(): Int = 42
- 14. fun answer() = 42
- 15. fun answer(): Int { return 42 }
- 16. // Parameters
- 17. fun greet(name: String): String { return "Hello " + name }
- 19. fun greet(name: String): String { return "Hello " + name }
- 20. fun greet(name: String): String { return "Hello $name" }
- 22. fun greet(name: String): String { return "Hello $name" }
- 23. fun greet(name: String, ): String { return "Hello $name" }
- 24. fun greet(name: String, greeting: String = "Hello" ): String { return "Hello $name" }
- 25. fun greet(name: String, greeting: String = "Hello" ): String { return "$greeting $name" }
- 26. // Calling a function
- 28. // Classes
- 29. class Game() { }
- 30. class Game() { fun join(user: UserName) { } }
- 31. val myGame = Game()
- 32. // Dependencies
- 33. class Game() { fun join(user: UserName) { } }
- 34. class Game(val logger: Logger) { fun join(user: UserName) { } }
- 35. class Game(val logger: Logger) { fun join(user: UserName) { this.logger.log("foo") } }
- 36. class Game(val logger: Logger) { fun join(user: UserName) { logger.log("foo") } }
- 37. class Game(private val logger: Logger) { fun join(user: UserName) { logger.log("foo") } }
- 38. // Neat Class Things
- 39. // Neato Constructor Options // Enums // Sealed Classes // Delegation // Properties data class Name(val first: String, val last: String)
- 40. // Null Safety
- 41. fun greet(name: String): String { return "Hello $name" }
- 42. fun greet(name: String?): String { return "Hello $name" }
- 43. fun greet(name: String?): String { return "Hello $name" } “Hello Ross”
- 44. fun greet(name: String?): String { return "Hello $name" } “Hello null”
- 45. fun greet(name: String?): String { return "Hello $name" }
- 46. fun greet(name: String?): String { return "Hello ${name.toUpperCase()}" }
- 47. fun greet(name: String?): String { return "Hello ${name.toUpperCase()}" }
- 48. fun greet(name: String?): String { return "Hello $name" }
- 49. fun greet(name: String?): String { if (name == null) { return "STRANGER DANGER" } return "Hello $name" }
- 50. fun greet(name: String?): String { return "Hello $name" }
- 51. fun greet(name: String?): String { return "Hello ${formatName(name)}" } fun formatName(name: String): String { return name.toUpperCase(); }
- 52. fun greet(name: String?): String { return "Hello ${formatName(name)}" } fun formatName(name: String): String { return name.toUpperCase(); }
- 53. fun greet(name: String?): String { return "Hello ${formatName(name)}" } fun formatName(name: String): String { return name.toUpperCase(); }
- 55. // Java Interop
- 56. import myutils.tableflip import java.time.LocalDate val now = LocalDate.now()
- 58. fun BoardGame.tableFlip(): String { return "(ノ°Д° ︵）ノ ┻━┻" } val game = BoardGame() game.tableFlip()
- 60. fun BoardGame.tableFlip(): String { return "(ノ°Д° ︵）ノ ┻━┻" } val game = BoardGame() game.tableFlip()
- 62. import java.time.LocalDate fun LocalDate.yesterday(): LocalDate { return minusDays(1) } val now = LocalDate.now() val yesterday = now.yesterday()
- 63. // Collections
- 64. val nums = listOf(1, 2, 3) nums.map( )
- 65. val nums = listOf(1, 2, 3) nums.map({x: Int -> x * 2}) nums.map({x -> x * 2}) nums.map() {x -> x * 2} nums.map {x -> x * 2} nums.map { it * 2 }
- 66. // DSLs
- 67. routing { get("/") { call.respondText("Hello, world!") } post("/register") { // do stuff } }
- 68. val routing = RoutingBuilder() routing.get( {call: Call -> call.respondText("Hello World!") } ) routing.post(/* do stuff */)
- 69. html { head { title { +"Demo" } } body { h1 { +"Welcome!" } a(href="/FAQ") { +"FAQ" } } }
- 70. // Kotlin & Me & You